Oxidative coloring methods and compositions have had tremendous significance for the coloring of human hair. Coloring takes place through the reaction of one or more primary intermediates with one or more couplers in the presence of a suitable oxidation agent. In particular, the oxidation agent is added to a mixture of one or more primary intermediates and one or more couplers shortly before application to the human hair. The oxidation agent then stimulates an oxidation condensation reaction between the one or more primary intermediates and the one or more couplers to form the colored dye molecules in situ on the hair.
For the purposes of this specification, the following lexicon shall apply. Oxidative dyes (sometimes called para-dyes) are the substances used as permanent hair dyes. These are, for the most part, colorless or faintly colored compounds which are transformed into a colored material in situ on the hair. When mixed with oxidizing agents these oxidative dyes produce colored compounds or colorants through a process of oxidative condensation. There are two types of oxidative dye intermediates which are used in combination to produce permanent hair colors, these are the primary intermediates and the couplers. In general, the oxidative dye intermediates are aromatic compounds belonging to several chemical families: diamines, aminophenols, aminonaphthols, phenols and naphthols.
Primary intermediates are aromatic compounds which are almost exclusively benzene derivatives, substituted by at least two electron-donor groups, such as amine or hydroxy groups, these being para or ortho to each other. This confers the property of easy oxidation. A primary intermediate combines with a coupler in an oxidative condensation reaction (sometimes called a coupling reaction) to form the colored dye molecules.
Couplers are also oxidative dye intermediates which are also aromatic compounds, and couplers are also almost exclusively benzene derivatives substituted by the same groups as the primary intermediates. However, couplers are substituted in meta position to each other. In this position it should be noted that the couplers do not have the property of easy oxidation. A coupler combines with a primary intermediate in a condensation reaction to produce the colored dye molecules.
Coupler-modifiers are, per the present invention, substances which are added to the oxidative condensation reaction in addition to the primary intermediates and the couplers as discussed above. It is not known how a coupler-modifier participates in the condensation reaction; but, it has been discovered that coupler-modifiers do affect the final hair color produced by a condensation reaction.
Oxidation agents are peroxide compounds which are added to a mixture of one or more primary intermediates with one or more couplers to stimulate the oxidation condensation reaction to occur quickly. The oxidation agent is added to the primary intermediate/coupler mixture shortly before applying the dye mixture to the hair.
In oxidative coloring, numerous primary intermediates have been employed. Examples include 1,4-diaminobenzene, 2,5-diaminotoluene, 3-methyl-4-aminophenol, N,N-bis-(2-hydroxyethyl)-p-phenylenediamine, and p-aminophenol. Similarly, numerous couplers, such as resorcinol, 4-chlororesorcinol, 1-naphthol, 2,4-diaminotoluene, 2,4-diaminophenoxyethanol, 2,5-dimethylphenol, methyl resorcinol, m-phenylenediamine, 2,6-diaminopyridine, and m-aminophenol, inter alia, have been used. Oxidation agents have included urea peroxide, melamine peroxide or hydrogen peroxide; however, hydrogen peroxide has been the preferred oxidation agent.
Chemical substances to be used for the coloring of human hair must meet numerous minimum requirements. For example, these substances must be toxicologically and dermatologically suitable for such use. Additionally, they must also provide the desired intensity of color and provide a broad palette of various color nuances. Further, good tolerances to light, and/or acid exposure, permanent wave treatments, and physical rubbing are required. In any event, the hair colorings should remain stable over a period of at least 4 to 6 weeks without negative influence from light, rubbing and/or chemical agents.
This large number of requirements has not been fully or satisfactorily met through the use of known oxidation hair coloring substances. This is particularly true for the phenolic couplers 1-naphthol, 2,5-dimethylphenol, m-phenylenediamine as well as derivatives 2,4-diaminotoluene and 2,4-diaminophenoxyethanol.